There is no visible grain size. Obsidian's colors are dark green to dark brown and black, also can show gold, green, yellow, blue and/or purple. When lava comes into contact with water and after it cools it forms obsidian. Some minerals found in it are Cristobalite, and Quartz. Obsidian forms above ground on earth's surface.
Some uses of obsidian are cutting tools, weapons, and for ceremonial purposes. Obsidian can also be used for craft tools and to make diamonds.
Obsidian's colors are dark green to dark brown and black, also can show gold, green, yellow, blue and/or purple.
When lava comes into contact with water and after it cools it forms obsidian.
Some minerals found in it are Cristobalite, and Quartz.
Obsidian forms above ground on earth's surface.
Obsidian can also be used for craft tools and to make diamonds.
Sources:
http://www.galleries.com/minerals/mineralo/obsidian/obsidian.htm
http://volcano.oregonstate.edu/education/facts/obsidian.html
http://en.wikipedia.org/wiki/Obsidian
http://www.google.com/images?q=obsidian
Made By: Seth Berg And Cody Arneson